Submarine Root Survey of Powered Cables


​​​​​​​​​​​​​​​​​​​Located in the South China Sea, Hainan Island is the smallest province of China and is the nation’s southernmost point. It is renowned for tropical climates, beach fronts and its wild mountainous inlands. In the city of Sanya, a tourist hot-spot, sits an array of luxury hotels alongside the attractive Yanoda Rainforest hiking trails, suspension bridges and waterfalls. Geographically, Hainan Island is separated from Guangdong’s mainland Leizhou Peninsula by the Qiongzhou (Hainan) Strait, a body of water and the main terminal of travel from island-to-mainland.

Hainan Island was once known locally as the ‘Power Isolated Island’ as all power was controlled and delivered from the island itself. However, the Fukang Line (power cables) were laid in June 2009 from mainland across the Qiongzhou Strait, to the island in order to back up the entire Hainan island power supply. The role of this four-cable line was fundamental to ending the ‘Power Isolated Island’ tag as it is now  responsible for the whole island’s power as a backup should there be a grid collapse in the on-island power supply network.

The Fukang Line requires an annual root survey to assess the condition, location and depth of burial of the cables in order to continuously support Hainan Island. This survey is an unprecedented challenge each year as the power supply needs to be turned off in order successfully survey, as well as being influenced by a number of pressures and factors. Traditionally, this survey work has been undertaken using tone injection systems alongside sub-bottom profilers so a seafloor map could be produced. The operation of this set equipment means that the cables could not be surveyed whilst powered but in turning the power off, the island is at great risk should any faults occur in the main power supply.​